This invention relates to the development of a metal-jacketed, non-hollow point bullet intended for law enforcement use which exhibits optimum penetration and more reliable and consistent expansion than hollow point bullets when fired through dry materials such as wallboard, plywood and heavy clothing, while maintaining 100% weight retention.
In December of 1988, the Federal Bureau of Investigation Academy Firearms Training Unit designed and implemented a special test protocol for evaluating the effectiveness of modern ammunition using various types of bullets. Each cartridge and bullet type submitted for testing was used in eight different test events. All of the tests ultimately entailed the penetration of blocks of 10% ballistic gelatin, with and without intermediate barriers in front of the gelatin. These tests included firing bullets into bare gelatin at a distance of 10 feet and through the following materials placed in front of the gelatin; heavy clothing, sheet steel, wallboard (gypsum board), plywood, automobile glass, heavy clothing at 20 yards, and automobile glass at 20 yards.
The FBI does not have a specific requirement for bullet expansion. The criterion is the volume of the wound. However, wound volume is a direct result of the rate and extent of bullet expansion. That volume is measured as the product of the extent of penetration and the frusto area resulting from the expansion. They grade sample ammunition, and the wound volume is one of the parameters used in reaching a purchasing decision. Ammunition with less than twelve (12) inches of penetration is usually not purchased. Penetration beyond eighteen (18) inches is not utilized in calculating the wound volume.
The FBI protocol is the most stringent test protocol ever devised. Many of the ammunition manufacturers soon discovered that the hollow point bullets, which they had at that time, produced very poor results in gelatin after passing through dry barriers. In an attempt to increase the robustness of their bullets, manufacturers developed bullet-weakening features to enhance post-dry-barrier expansion. These efforts were met with minimal success because ultimately, performance was still severely limited by the hollow point concept itself. Even today, many of the best hollow point bullets available perform only marginally well when tested using the FBI protocol.
Hollow point bullets rely on simple hydraulic action to initiate radial expansion. This hydraulic action occurs as fluid enters and fills the bullet""s nose cavity upon impact with a fluid-based target. Because of its dependence on fluid and the actual filling of its nose cavity with fluid, a hollow point bullet expands poorly, if at all, when impacting dry, intermediate targets such as wallboard, plywood and heavy fabric. In short, without the immediate presence of fluid, the hollow point bullet""s nose cavity will clog severely after encountering almost any dry media. The material producing the worst effect on hollow point bullet performance is wallboard. This is because the gypsum dust has a tendency to pack tightly into the nose cavity which essentially transforms the bullet into a solid-nosed projectile which will, at best, exhibit minimal expansion due to the inherent strength of the core metal comprising its cavity wall. Essentially, when a dry media is substituted for fluid in its cavity, the hollow point bullet is unable to take advantage of simple hydraulics. By utilizing a completely different expansion technology, the bullet described hereinafter overcomes the inherent limitations of hollow point bullets.
The design of our bullet is characterized by a collapsible nose portion. This type of bullet provides a limited but adequate degree of expansion while penetrating to the degree demanded by the FBI. While doing so, it retains substantially 100% of its weight.
The above bullet is comprised of a jacket of malleable metal, such as one formed predominantly of copper, and has a closed conventionally tapered nose portion and a rearward cylindrically shaped sidewall which is preferably open at its rear end. The nose portions have circumferentially spaced weakened areas, which extend axially of its nose-defining wall and are preferably formed by deep internal scoring, although external scoring may be utilized. Compressed within the closed forward end of the jacket and bearing against the interior surface thereof is a soft rubber or other polymer core, the rear portion of which terminates at, ahead of, or rearward of the inflection point. This inflection point is located at the juncture of the tapered nose portion and the forward end portion of the cylindrical wall of the jacket. Mounted within the cylindrical wall of the jacket is a metal core which bears against the rear end of the rubber core in compressing relation thereto. Preferably, the rear end of the metal core terminates adjacent the rear end of the cylindrical wall of the jacket, and the terminal portion of said wall thereat is crimped inwardly to lock the metal core therewithin in compressing relation to the rubber core. The forward end surface of the metal core is preferably recessed with a concave or dished out configuration. The metal core is preferably made of pure lead or some other metal which is softer than the metal of which the jacket is made. Another suitable material would be metals mixed with polymer binders, such as a tungsten/polymer mixture. This core may also be made of a polymeric material of suitable hardness.
When the above-described bullet strikes and penetrates a target which is of soft to medium hardness, the nose portion collapses axially, which increases the pressure upon the rubber core. This causes the latter to rupture the nose-defining portions at the scored or otherwise weakened areas, and to separate along the scoring lines. As this occurs, the metal of the nose portion and the rubber core expand substantially in a radial direction, while the cylindrical wall and the metal core therewithin remain directly therebehind, and retain substantially 100% of their weight.
The above bullet will penetrate such materials at least twelve (12) inches and the nose portion will expand radially in excess of 50%, while retaining its weight at approximately 100%. Actual measurements show the radial expansion as great as 70%. Both the metal core and the rubber core will remain encapsulated by the metal jacket.
Our bullet will penetrate ten (10) layers of heavy denim cloth and still expand adequately in 10% ballistic gelatin. No conventional hollow-point bullet extant can duplicate or exceed this type of performance.
The front core is preferably made of rubber, urethane, silicone, or one of a substantial number of plastics, such as fluorocarbons, polycarbonates, polypropylenes, polystyrenes, polyethylenes, PVC(trademark), silicone rubber, Nylon(trademark), or vinyl acetate, each of which has a hardness within a range of Shore A-20 to Rockwell R-122.
The rear core is preferably formed of a metal which is softer than that from which the jacket is made. Pure lead is the preferred material. Other suitable metals are copper, zinc, iron, steel, tin, lead, tungsten, copper, bismuth, green or sintered powdered metals, or alloys thereof. Another suitable material would be metals mixed with polymer binders, such as a tungsten/polymer mixture. This core may also be made of polymeric material of suitable hardness.
The bullet ogive can be frusto-conical in shape or it may comprise a curving ogive.
It is a general object of our invention to provide a captive soft-point bullet which will overcome the disadvantages of a hollow-point bullet and will thereby out-perform all extant hollow or soft-point bullets with respect to uniform, reliable expansion and adequate penetration when fired into soft to medium hard targets after first having passed through dry intermediate barriers such as wallboard or heavy clothing.
A further object is to provide a captive soft-point bullet which will expand radially to a relatively large diameter when fired into soft to medium hard targets and still penetrate to a depth of at least twelve (12) inches.
Another object is to provide a captive soft-point bullet which, when fired into soft to medium hard targets, will penetrate to at least twelve (12) inches while expanding radially to at least a 50-70% extent.
A still further object is to provide a captive soft-point bullet which provides 100% weight retention after first passing through intermediate barriers and thereafter impacting a soft is to medium hard target.